This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-125911, filed May 6, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a (film) camera with an image pick-up device mounted thereon and, in particular, the camera which effects a high-speed and wide-scope auto-focusing (AF) detection using an image pick-up area of an image pick-up device.
Usually, the camera for taking a picture with the use of a film was not able to confirm a taken picture at a site or field because it has to be developed and printed.
Therefore, a camera has been proposed as set out below. That is, an image pick-up element, such as a CCD, is mounted in the camera body and a portion of a light beam directed toward the film at a time of taking a picture is branched to allow it to be received on the image pick-up device. In this way, an image is picked up by the image pick-up device at substantially the same time as at a light exposure time and a corresponding image equivalent to a picture taken on the film is stored and reproduced at that place, so that it is possible to confirm the taken picture as substantially the same image as that taken onto the film.
In these types of cameras, for example, JPN PAT APPLN KOKAI PUBLICATION NO. 7-281271 has proposed the technique of performing a contrast AF by using, as an AF control sensor, an image pick-up device mounted for the confirmation of a taken image.
Further, in this technique, it is possible to display, on a monitor, not only the taken image but also fit/unfit focus states when it is used to control the light exposure amount and AF and, by dividing an image displayed on the monitor into a plurality of areas, display a fit/unfit state at each area by a color display method for example.
Further, JPN PAT APPLN KOKAI PUBLICATION NO. 7-281080 discloses the technique for realizing a phase difference AF by providing two range-finding light receiving areas near a light receiving element area for a monitor of an image pick-up device provided within a finder and detecting a phase difference signal of a subject image.
In the technique of the JPN PAT APPLN KOKAI PUBLICATION NO. 7-281271, hill climbing control has been adopted for contrast AF. This hill climbing control presents a problem that it is hard to set a focus against a fast-moving subject. As a result, an out-of-focus state occurs against the fast-moving subject or there is a risk that no proper shutter release moment will be obtained.
For the phase difference AF of the PUBLICATION NO. 7-281080, a light receiving element area for monitoring the image pick-up surface and light receiving element area for detecting the AF area individually provided on a light receiving light surface of the image pick-up device and the size of the image pick-up device becomes greater. If, therefore, a detection area is to be made broader so as to enhance the accuracy of the AF control, then the light receiving surface has to be made larger and the image pick-up device becomes larger. Thus, there is some restriction.
Since, further, a light beam from a picture-taking lens system is usually branched by a half-mirror so as to take an image onto the image pick-up device, an amount of light reaching the film is reduced to a half level and, at a time of taking a picture, the substantial sensitivity of the film becomes lower and the shutter speed for a proper light exposure is slowed, so that camera shaking is liable to occur.
The object of the present invention is to provide an AF-controlled camera which includes an image pick-up device and display monitor capable of confirming an image equivalent to a film-shot image just after the taking of a picture, detects a phase difference over a wider area with the use of the image pick-up device for AF control, and can attain an accurate, fast-speed focus setting without increasing the size of the image pick-up device.
The present invention provides a camera capable of forming a subject image onto a film with a light exposure and picking up the subject image by an image pick-up device and including: a picture-taking optical system for forming a subject image onto a film surface, a reflection mirror for reflecting at least a portion of a subject light beam passing through the picture-taking optical system, a re-imaging optical system for allowing the light beam which is reflected on the reflection mirror to be re-imaged on a light receiving area of the image pick-up device, a liquid crystal shutter provided between the re-imaging optical system and the image pick-up device and allowing the subject light beam which passes through the re-imaging optical system to be pupil-divided, the liquid crystal shutter having a first light transmissive state in which a light beam of a first area of the re-imaging optical system is passed and a second light transmissive state in which a light beam of a second area of the re-imaging optical system different from the first area is passed, a liquid crystal control circuit for setting the liquid crystal shutter at different timing to the first and second light transmissive states, and an electric circuit for outputting a signal relating to a focus state of the picture-taking optical system by a phase difference system on the basis of an image pick-up device output in a first light transmissive state and an image pick-up device output in a second light transmissive state.
Further, the present invention provides a camera capable of forming a subject image onto a film with a light exposure and picking up the subject image by an image pick-up device, and including: a picture-taking optical system for forming a subject image onto a film surface, a reflection mirror for reflecting at least a portion of a subject light beam passing through the picture-taking optical system, a re-imaging optical system for re-imaging the subject light beam which is reflected on the reflection mirror onto a light receiving area of the image pick-up device, a liquid crystal shutter provided between the re-imaging optical system and the image pick-up device and allowing the subject light beam which passes through the re-imaging optical system to be pupil-divided, and an electric circuit for outputting a signal relating to a focus state of the picture-taking optical system by a phase difference system on the basis of an output of a light receiving area of the image pick-up device on which the subject light beam divided by the liquid crystal shutter is re-imaged.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.